Corona free multiplier



June 16, 1953 B. w. SMITH CORONA FREE MULTIPLIER Filed June 14, 1951 INVENTOR Ber/74rd Winn/'3} ,ZQ VVefer ATTORNEY Patented June 16, 1953 CORONA FREE MULTIPLIER Bernard W. Smith, Winston-Salem, N. 0., assignor to WesternEl'ectric Company, Incorporated, New York, N. Y., a corporation of New York Application June-14", 1951, Serial-No. 231,541

9 Claims. 1

This invention relates to electrical instrumentmultipliers and more particularly to a multiplier having corona free construction. I

In making voltage measurements, a currentsensitive meter is placed in series with a multiplier. to produce a voltage indicator which Will include a desired range of voltages. At high voltages, the customary meter and multiplier combination is unsatisfactory since corona, resulting from the high potential gradient, introduces a shunt path to by-pass the indicating meter. Eflorts to eliminate the losses due to corona discharge have been unsuccessful or, at best, have produced bulky and unwieldy devices.

An object of the present invention is to provide an instrument multiplier that can be utilized in high voltage circuits without incurring any losses because of corona and which can be used for accurate voltage determinations in a high voltage range.

In accordance with one embodiment of the invention, there is provided a multiplier having a plurality of carbon resistors which are interconnected by smooth rounded supporting members and are suspended from these supporting members within a group of insulating tubes. The insulating tubes are positioned within a cylinder made of an insulating material and are held in spaced relation by fiber discs fitted within the cylinder for that purpose. The cylinder is closed at both ends by rounded metallic end members which also serve as electrical terminals for the assembly. The unit is then impregnated with an oil which has a high dielectric strength and the assembly is mounted vertically on a base. of insulating material. All of the parts are machined to have round edges and polished to remove machine marks so as to reduce the tendency toward atmospheric discharge at high voltages.

A complete understanding of the invention may be obtained from the following detailed description taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a longitudinal section illustrating one embodiment of the invention.

Fig. 2 is a cross-sectional view taken along line 22 of Fig. 1 showing the electrical interconnection of the tubes of resistors;

Fig. 3 is an enlarged detailed view of a supporting connector illustrating the suspension of resistance elements within one of the tubes;

Fig. 4 is a fragmentary perspective of an end of one of the tubes and showing a slot for retaining a supporting connector;

Fig. 5 is a fragmentary view taken along line- 55 of Fig. 2' illustrating the supporting means for the tube positioning discs; and

Fig. 6 is a partial sectional view taken along line 6-6 of Fig. 1 showing means for establishing an electrical connection in the base.

Referring now to the drawing wherein like reference numerals designate the same parts throughout the several views, and more particularly to Fig. 1 wherein an insulating cylinder 2I of a ceramic material is closed at both ends by rounded metallic end closures 22 and 23 threaded thereon, terminals 24 and 25 are fitted into apertures in the end closures 22 and 23, respectively, and are secured in place by solder fillets. The upper end ofterminal 24 is threaded into a metal cap member 26 which is adapted to be connected to a plug I9 from an electrical apparatus being tested.

End closure 23 rests upon an insulating base 27 which has a metallic insert 28 which serves as an electrical conductor (Fig. 6) and has a kilovolt meter 29 connected thereto.

The cylinder 2I has mounted within it a resistor assembly including insulating discs 20 which are notched to engage vertical supporting members I I correspondingly notched as shown in Fig. 5. Insulating tubes I2 are tightly fitted into spaced apertures in the discs 20 and thus are held in predetermined spaced relation within cylinder 2 I.

A plurality of electrical resistors I3 are suspended within each tube I2 and are connected in series by small rounded metallic connectors I4 which have a central bore into which the terminal wires of two resistors are inserted from opposite ends. Solder is then applied to the connector I4 and it is burnished to remove all sharp corners and rough edges.

The series chains of resistors I3 in the various tubes I2 are interconnected in series by smooth rounded supporting connectors I5 which rest in notches on the insulating tubes I2 (Figs. 3 and 4). Terminal leads I6 at the ends of the entire series chain of resistors I3 are connected to the terminals 24 and 25 by insertionin a central bore thereof. and secured therein with a solder seal. Attached. to. each terminal leadv I6 is a metallic disc I! which. maintains the resistors centrally oriented within the tubes I2.

The cylinder H is evacuated and vacuum impregnated through apertures I8 in the end closure 22 with a fluid of high dielectric properties, such as transil oil, after which said apertures are sealed with solder.

members for sealing said receptacle,'a .plurality of hollow insulators retained in spaced relation within said receptacle, a plurality 'of' resistors within said hollow insulators and electrically interconnected, and a terminal retained in each member connected to the resistors and adapted for connection to the electrical instrument.

2. In an electrical instrument multiplier, a receptacle of insulating materiaL'roun'ded metallic end members for sealing saidreceptacle, a plurality of hollow insulators retained in spaced relation within said receptacle, a plurality of series connected resistors retained within said hollow insulators and connected to said end members, and a dielectric fluid substantially filling said receptacle to prevent corona discharge at high voltages.

3. man electrical meter multiplier, a cylinder of insulating material, metallic members for closing the ends of said cylinder, a plurality of hollow insulators, means for retaining said hollow insulators in a predetermined spacedrelationship within the cylinder, a plurality of series connected resistors within said hollow insulators and connected to said end closing members, and a dielectric fluid substantially filling said-cylinder;

4. A corona free multiplier comprising a cylinder of insulating material, members of conducting material for closing the ends of said cylinder, a plurality of spaced insulating tubes positioned within said cylinder, a plurality of resistance elements connected in series and positioned within said tubes and connected to said end members, and a dielectric fluid substantially filling the said cylinder.

5. In an electrical instrument multiplier, an insulating cylinder, a plurality of hollow insulators, means for retaining the hollow insulators in a predetermined spaced relationship within the cylinder, a plurality of resistors, connectors having smooth rounded surfaces for interconnecting the resistors in series within the hollow insulators, metallic members connected to the resistors and having smooth and curved surfaces for closing the ends of said cylinderand to prevent corona, and a dielectric fluid substantially filling the closed cylinder.

6. A corona free multiplier comprising a cylinder of insulating material, closure members of conducting material for sealing the ends of said cylinder, a plurality of spaced insulating tubes positioned within said cylinder, a plurality of re- '4 plier, a cylinder of insulating material, a plurality of insulating tubes, means for retaining the insulating tubes in a predetermined spaced relationship within said cylinder, resistors of predetermined value, metallic connectors having smooth rounded surfaces for connecting said resistors in series within the insulating tubes, smooth rounded metallic connectors supported by the tubes for retaining the series of interconnected resistors therein and interconnecting them from tube to tube, and metallic end members connected to the resistors and having smooth rounded surfaces for closing the ends of said cylinder.

8. In an electrical instrument multiplier, a smooth ceramic cylinder threaded at each end, notched supports positioned against the internal wall of said cylinder, insulating discs having notched portions for engagement with the notched supports and having spaced apertures, insulating tubes positioned within the spaced apertures of the discs, resistors of predetermined value connected in series within each tube, smooth rounded connectors for supporting the series of interconnected resistors in the tubes and for interconnecting them from tube to tube, means for supporting the connectors at predetermined ends of said tubes, smooth rounded metallic end closures threaded onto the ends of the cylinder, a terminal secured in each of said end closures, means for connecting one of the two ends of the interconnected resistors to one of the terminals and the other end thereof to the other terminal, and a dielectric substantially filling the ceramic cylinder.

9. In an electrical instrument multiplier, a smooth ceramic cylinder threaded at each end, notched supports positioned against the internal Wall of said cylinder, insulating discs having spaced apertures, insulating tubes positioned within the spaced apertures of the discs, resistors of predetermined value connected in series Within each tube, smooth rounded connectors for supporting the series of interconnected resistors in the tubes and for interconnecting them from tube to tube, means for supporting the connectors at predetermined ends of said tubes, smooth rounded metallic end closures threaded onto the ends of the cylinder, metallic terminals connected to the ends of the series of resistors and secured in said end closures, a base, a conductor secured in said base and connected to the terminal in one of said end closures and connected to the electrical instrument to determine the voltage range thereof, and a dielectric fluid substantially filling said cylinder.

BERNARD W. SMITH.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Country Date Germany Jan. 9, 1915 Germany May 20, 1930 Number Number 

